diff --git a/tests/atf_python/sys/net/vnet.py b/tests/atf_python/sys/net/vnet.py
index 6da5f262599..68c8ce4e0cb 100644
--- a/tests/atf_python/sys/net/vnet.py
+++ b/tests/atf_python/sys/net/vnet.py
@@ -134,7 +134,7 @@ class VnetInterface(object):
         self.run_cmd(cmd)
 
     def enable_ipv6(self):
-        cmd = "/usr/sbin/ndp -i {} -disabled".format(self.name)
+        cmd = "/usr/sbin/ndp -i {} -- -disabled".format(self.name)
         self.run_cmd(cmd)
 
     def has_tentative(self) -> bool: